Clay Pot Irrigation, an ancient, efficient watering system, is making a huge comeback as gardeners are learning about it and seeing its value as an alternative to hoses and sprinkler systems. Very simply, clay pot irrigation consists of burying an organic unglazed clay pot, called an OLLA, in the ground up to the neck. The olla is filled with water and plants are planted outside the olla. A process called soil-moisture tension occurs, watering the plants as needed, saving up to 70 percent in water use. A DSO OLLA can water an 18 inch radius for three to five days, in a garden, raised bed or container. Suggested retail price: $35.